1. Field of the Invention
The invention relates to the field of the compression and decompression of color video digital data.
2. Prior Art
Numerous techniques are known in the prior art for compressing and decompressing digital data. For example, see copending application, entitled VIDEO COMPRESSION ALGORITHM, Ser. No. 441,333, filed 11/22/89, which is a continuation of Ser. No. 084,309, Filed 08/11/87, now abandoned, and assigned to the Assignee of the present invention.
In some instances, the data is compressed in a uniform manner block-by-block or frame-by-frame. That is, by way of example, m bits of compressed data are used to represent each n.times.n block of pixel data. In other methods, such as the one used in the present invention, the degree of compression is a function of the characteristic of the video data sought to be compressed. Again, by way of example, it is common to represent a plurality of adjacent pixels of the same color.
As will be seen, the present invention teaches an adaptive compression/decompression method which examines the color video data, block-by-block, and then determines the type of compression to be used for each block. One of types of compression used in the present invention is similar to that described in U.S. Pat. No. 4,580,134. In general, this type of compression takes a 4.times.4 block of pixel data and encodes it into two colors and a 16 bit bitmap. The bitmap on a decompression indicates which of the two colors is to be used for each pixel. In the present invention, this type of compression is extended in a novel manner to provide anti-aliasing for these blocks.
Other prior art known to Applicant is disclosed in "Two Bit/Pixel Full Color Encoding", Siggraph '86, No. 4, 1986, beginning at page 215 and U.S. Pat. No. 4,743,959.